Say less, do more.

Absolutely correct and sound advice. I’m experiencing this first-hand with Quizzardous!* - in hindsight, perhaps it would have been a better idea to just work on it, minus all the hype.

Announcing a project early has its pros and cons - but mainly more of the latter.

Pros:

Announcing a project or telling friends about an idea might significantly change the idea itself. This is good. (refer to Sivers on the worth of ideas) Instagram initially started off as a Gowalla style app but changed into what it is today when Kevin Systrom shared the idea with his team.
Most developers are mediocre. So are you (statistically speaking.) As am I. Mediocrity means that you need the help of others to achieve what a good developer might be able to achiveve alone. John Carmack might be able to create an awesome 3D engine all by himself, but you are no John Carmack. Having a good team lets you bounce ideas off them, and inspires you to work harder, for the rest of the team (provided it’s a good team!)

Cons:

Expectations - If you announce your idea publicly, people expect the idea to evolve and to grow. Some ideas just aren’t good enough. This makes it that much harder for you to kill them off.
If you’re one person working on one idea, you should be doing the bare minimum number of things that you need to do in order to execute it. Announcing your project on social platforms and then “keeping in touch” with your followers is just extra work.
Deadlines: Ideas have no deadlines. They may take anywhere from a second to a lifetime to develop completely. By announcing your project, even if you don’t mention when it’s launching, you’re implicitly saying that “it’s coming soon.” It may not. Or if you follow the first point, it may not come at all.
You may lose the first mover advantage to a team that is larger than yours.
etc etc. Too many things to list here.
The takeaway is that you should find a small group of around three to four people who can understand your idea and help you improve upon it. No one else should get a word of it until you’ve executed your idea or plans. For bonus points, use: “I could tell you, but then I’d have to kill you.”

*Don’t worry, though - we aren’t far away from shipping. We’ve got the basics covered, it’s just waiting for some spit and polish now.